Variable ratio photoelectric engraving machine



Feb. 24, 1959 F. P. WILLCOX ETAL VARIABLE RATIO PHOTOELECTRIC ENGRAVING MACHINE Filed May 1o', 19524 4 Sheets-Sheet 1 AMPLI FER TRANSMISSION 46 Fvg /l/g' 2 MODUL/WOR INVENTORSI ORNEY Feb 24, 1959 F. P. wlLL'cox ETAL 2,875,275

VARIABLE RATIO PHoToELEcTRIc ENGRAVING MACHINE Filed May 1o, 1954 4 Sheets-Sheet 2 P. W/Lcox WELANETZ; RJ. AUTERE 5 J. S. HELLEN,

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Feb. 24, 1959 F. P. wlLLcox ET AL VARIABLE RATIO PHOTOELECTRIC ENGRAVING MACHINE Filed May 10, 1954 4 Sheets-Sheet 3 IIIIIHIH l,

gms/Mom: FP W/LLcox; .FWELANETZ J EN:

RJ. AUTE'QE J. S. HELL Feb. 24, 1959 F. P. wlLLcox ET AL 2,875,275

VARIABLE RATIO PHOTOELECTRIC ENGRAVING MACHINE Filed May 1o, 1954 4 Sheets-Sheet 4 INVENTORS: EP. W/LLcox; E WELA/s/Ezj BY X/m A TTORN@ Y United States Patent() M VARIABLE RATIO PHOTOELECTRIC ENGRAVING MACHINE Camera and Instrument Corporation,` a corporation of Delaware Application May 10, 1954, Serial No. 428,606

21 Claims. (Cl. 178-6.6)

This invention pertains to automatic engraving machines, and particularly to engraving machines of the type which provide an engravedv plate or the like for printing purposes, directly from original subject matter such as a photographic positive or negative to be reproduced by a printing process. More particularly, the present invention deals with an improved machine of this type in which any desired size enlargement or reduction (within the limits of the machine design) can be obtained as between the original subject matter and the reproduction or engraved plate.

Photoelectrically controlled engraving machines of the general type with which the invention is concerned have been proposed in various forms. One practical and successful machine of this type, manufactured by the assignee of the present invention, is illustrated in U. S.

Patent No. 2,575,546 to Boyajean, issued November 20,

1951. In that machine, a photograph or other original material to be reproduced is wrapped about a cylinder and subjected to a helical path scanning operation to generate an electric signal which controls an engraving tool operating upon a blank engraving sheet wrapped about a second cylinder driven synchronously with the first cylinder. For further details of this known machine, reference may be made to the cited patent.

Modern graphic arts techniques, including letterpress, offset work, gravure and also high speed production of large editions of printed matter such as newspapers and magazines, impose severe requirements as to speed, flexibility and other factors upon the procedures used in preparing screen plates for the engraving of pictorial (and other) subject matter to be reproduced. One limitation which has been observed with respect to the cylinder engraving machine referred to above is that the engraving plate produced has necessarily been of the same size scale as the original subject or photograph. Theoretically, of course, it is possible to utilize a pair of y 2,875,275 Patented Feb. 24, 1959 both enlargement and reduction, between selected limits in each case, by means which are simple and reliable and which can be adjusted readily to provide any desired finished size of the engraved plate.

A further object of the invention is to provide a machine of this type in which the ratio of length to width cylinders of different diameters, driven together, to

the diameter of at least one cylinder must be altered in Y the same ratio as the size ratio of their speeds, or a set of different cylinders employed. Not only is this impractical, particularly where a large range of ratios is required, but the gearings themselves are complicated and expensive, if the necessary precision of image dot placement is to be maintained. Also, such a machine would still have the limitation that only flexible originals could be reproduced, because of the necessity for cylindrical scanning in this type of device.

It is accordingly a principal object of the present invention to provide a machine which will produce automatically and at a desirable speed of operation, an engraved plate suitable for use in the printing process, and having any desired size relationship to the original subject matter. The machine to be described provides for alteration can be adjusted independently, to provide, where desired, a degree of systematic distortion, either compression or expansion, so that the enlargement or reduction may be different for the two directions, either to accommodate a printing space of particular dimensions, or to produce a degree of anamorphosis as is sometimes wanted in printed matter.

Still another important object of the invention is to provide a machine in which the above results are obtained without limitation of the original subject matter toforms which can be Wrapped around a cylindrical support. Thus, the invention provides for reproduction from either tiexible or rigid original matter, since the material need not be curved but may remain flat during the engraving process. The satisfactory accomplishment of this object also facilitates the employment of i originals which are quite small in size, so that even when they are flexible, diiculty would be encountered in securing them about the small cylinder that would be needed.

Yet another object of the invention is to provide a machine having the above features and in which provision is also made for obtaining finished engravings having different screen patterns, such as patterns providing diierent numbers of dots per inch or per square inch, to accommodate different printing techniques, to meet diverse standards of reproduction quality, or in accordance with the paper and inks to be employed in the printing process.

An ancillary object of the invention is to provide such a machine in which the desired angular or diagonal pattern of engraved dots on the plate is obtained by improved and simplified means as compared with prior machines of this type.

Finally, the present invention provides the above features and advantages in a structural organization which is compact and of relatively small size, and in which the controls and adjustments are grouped and located for facile and etlicient operation.

With the above considerations and objects in mind, the invention itself will now be described in connection with a preferred embodiment thereof given by way of example and not of limitation, and with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of the entire machine of the invention, showing the general relationship of its major components,

Fig. 2 is a schematic and block diagram illustrating the functional operation of the device.

Figs. 3 and 4 are exploded isometric views of the major mechanical parts of the machine, with certain parts broken away for clarity, and so drawn that the figures can be read as one by placing Fig. 4 to the right of Fig. 3 in slightly overlapping relationship,

Fig. 5 is a fragmentary sectional view taken along the line 5 5 vof Fig. 3 of the drawings, showing the principal parts concerned with production of the desired diagonal dot pattern.

Fig. 6 isa fragmentary schematic view in elevation of certain parts of the mechanism of Fig. 3, drawn to a larger scale for clarity, and

Fig. 7 is an enlarged perspective view showing certain details of the scanning aperture control mechanism of the invention.

Referring now to Figures l and 2 of the drawings, and first to Fig. l alone, the general arrangement of the apparatus is shown. Numeral 10 designates a casing or housing in which are contained the principal electrical circuit elements, amplifiers and the like required for the machine, and which serves also as a support for the major manipulative parts. Thus, the housing 10V is surmounted by a machine table or top plate l2 carrying a horizontal guide rail 14 upon which is slidably mounted the carriage 16 on which are supported the engraving head 18 and optical parts 20 constituting a stroboscopic illuminator and microscope for viewing the engraving during initial preparation or as the work proceeds. As in the prior patent referred to above, the sheet being engraved is wrapped around a cylinder 22 mounted for rotation between end bearings carried by the tail stock assembly 24 vand the machinery casing 26, both of which are mounted'upon the table 12 and at opposite ends of the guide rail 14.

The parts which have just been referred to are substantially identical, with differences later to be described, with the corresponding parts of the prior patent, and they serve to produce the desired engraving from electric signals obtained from a scanning operation which is carried out by apparatus quite different from the prior patent, and the parts of which will now be enumerated.

Since it is desired to make engravings with varying degrees of enlargement or reduction from originals which may not be in flexible condition, provision is made for supporting the original copy 2S upon a at rigid table 30 mounted for longitudinal sliding motion upon suitable guides within the housing l. By means to be described, the scanning operation is preferably started with the copy mounted on table 36 in its most extended condition, and proceeds as the table is withdrawn into housing l' by mechanism to be described'below. As indicated in Fig. l, the scanning is accomplished in zig-zag fashion, a line at a time crosswise of the table 30, and the region being Ascanned at any one table position is illuminated as by lamps mounted above the moving table upon the top plate 12'and provided with suitable reectors as generally indicated at 32 to throw their light downwardly and concentrated upon a laterally extending zone or strip of the original 28.

A scanning head containing the necessary optical parts and mechanical elements for the scanning operation is indicatedV generally at 34, and this head is energized mechanically from the mechanism housing 26 by means to be described.

A more complete idea of the operation of the machine is furnished by Fig. 2. Here, the shaft carrying the cylinder 22 is indicated by numeral 36, and is rotated by a transmission 26 from a motor, not shown. The transmission 26 has an output shaft 3S to which is secured a wheel driving an endless belt 40 which passes around a second wheel 42. To one portion of the endless belt (actually an inextensible metallic ribbon) is secured .a clamp 44 connected with the carriage 16 carrying the engravingv transducer, so that as shaft 36 rotates, the carriage 16 is translated longitudinally to engrave in a spiral pattern a sheet carried by cylinder 22. This part of the arrangement is generally the same as that of the patent referred to above. So .thata test engraving can be made while cylinder 22 is rotating butl with carriage i6 stationary, shaft 38 can be disengaged by a knob to. be described below.

Transmission 26 also drives a shaft 45 carrying a tape wheel 46 about which another and similar endless belt 48 is wrapped, being held in taut condition by a parallel wheel at thefar end of the tape travel. The copy table 30 issecured to one reach of the belt or tape 48, and will therefore be drawn into the housing progressively at a speed synchronized with the rotation of shaft 36. As the table 3G moves inwardly, a portion 36 of shaft 36 to the left of transmission 26 transmits (via a clutch 50) rotation to shaft 52 which drives the mechanism in the scanning head 34 to .cause reflector 54 to oscillate through an arc of predetermined but adjustable size. Suitable optics are provided so that at any instant the light reflected from only a minute spot of the original copy will be directed by mirror 54 to the scanning photocell 56 whose output principally determines the distance to which the engraver mechanism 18 drives its stylus into the plastic sheet being engraved, the sheet of course being wrapped about cylinder 22.

The portion 36 of shaft 36 has secured thereto a drum 58 forming with other parts a tone generator, and whose periphery carries a plurality (herein three) of tracks which may for example be :formed as regular series of magnetically permeable teeth to produce in cooperation with suitable pick-up heads, respective fixed-frequency tone signals used to modulate the amplied output from scanning photocell 56 to produce an engraved pattern consisting of regularly spaced engraved dots, as opposed to the continuous engraved groove which would otherwiseresult. The proper record track or tooth series onV drum 5S is selected manually or automatically in accordance with the desired screen spacing of the engraving.v The manually operated clutch 50 is con-` nected between thedisc 53 or. shaft portion 36 and. shaft 52, so that during initial adjustment or setting up of the apparatus, the drive for the scanning gear'34 may be disconnected; a clutch to be described operates to disconnect the drive of table 39. With both clutches disengaged, the machine operates to provide a photocell output representative of a particular selected spot or spots on the original copy. By energizing the main drive motor with these clutches disconnected, it is thus possible for a marginal portion of the plastic sheet to be engraved, and such test engraving inspected, for particular selected values of highlight vand shadow regions in the original copy. Since clutch 50 is to the left of drum 58, the screenmodulating signals from drum S will continue to be produced during this initial machine adjustment period.

Fig. 2 also illustrates schematically the general oW of signal intelligence in the apparatus. The scanning signals from the photocell 56 are conveyed to an amplifier 60 and the amplilied product is applied to the modulator 62 where the tone signals from drum 58, suitably amplilied, are added to provide an output to the transducer on carriage 16, which output includes components both of the scanning signals and the constant frequency screen modulation tone from the `drum S8.

The principal parts of the machine, especially the mechanical parts, are best shown in the exploded perspective views of Figs. 3 and 4, which can be read as a single ligure by placing Fig. 4 to the right of Fig. 3 witha slight overlap. The detailed description of these parts, however, will best be followed after a brief review of the relations which must be maintained between the parts.

In order to accommodate printing operations which employ different .page sizes and hence diierent dimensions of the engraved plate, it is desirable to arrange the machine so that a smaller'piece of plastic may bc used to produce the smaller plates, and a larger piece for the larger plates. This arrangement not only conserves the plastic material but minimizes the time required for engraving ,when a smaller plate isdesired, and is generally more suitable Where a large range of sizes of reproductions is to be produced by the machine. Thus, in the embodimentV shown herein, there may be one cylinder 22 which will be run at a lower speed such as 33 R. P. M., and which may have a diameter of about 4 inches, and a smallercylinder which will run at a higher speed of 50 R. P. M. and may have a diameter of about 2.9 inches. These cylinders would be suitable for preparing final engravings of about 8 x l0 inches and 1l x 14 inches, but obviously other cylinders may be employed to suit the requirements of the printing process in which the plate is to be employed. For-.either cylinder, the tone generating 'drum 58 must be operative, but must furnish the correct number of dots (or tone cycles per drum revolution) for the four possible combinations provided by screen spacings of 85 and 120 per inch (in the particular machine being described) and the two values of engraving cylinder diameters. Cylinder diameters and speeds can 'conveniently be chosen so that one of the tone tracks on drum 58 provides the proper number of cycles per drum revolution to produce 120 screen engravings with the small cylinder and also 85 screen engravings with the large cylinder. Thus, only three tone tracks are required to satisfy the four possible combinations mentioned above.

Another important function which should be borne in mind is the correction for the slight variation in the distance from the original copy to the scanning reflector when the scanned spot is at either lateral edge of the original, as compared with the distance from the copy to the reflector for a scanned spot on the longitudinal center line of the original. While scanning arrangements are known which compensate for this difference in path length, it is also necessary, in the present machine, to be able to adjust the actual total arc through which the scanning path moves in going from one lateral extremity of the original to the other. The mechanism of Fig. 3 solves this problem in a very satisfactory manner.

It may be repeated here that the enlargement and reduction obtained is in no sense a matter of image magnification or reduction as performed in ordinary optical projection apparatus. The distance from copy table 30 to the scanning reflector axis is fixed, and of course the distance from the reflector axis to the scanning photocell is also fixed. The scale change is accomplished purely by alteration in the limits of the scanning arc in relation to the constant angular velocity (rotation) of the engraving cylinder, and by a concomitant adjustment in the speed of travel of table 30 in relation to the steady rate of travel of the engraving head along the cylinder 22.

An important advantage of the scanning system described lies in its freedom from the space requirements of ordinary optical enlarging and reducing equipment of the projection type which depend upon the production of a focussed image of the original to a desired size, followed by scanning of the said image. In order to produce a full size engraved plate from an original as small as (say) one by one-and-a-half inches in size, corresponding to a normal color photograph on 35 millimeter film, the enlargement ratio of 8 to 1 has been incorporated in the machine illustrated. To accomplish this enlargement in a machine capable also of working from full size originals of say 8 by 10 inches or greater, a conventional optical system would be enormous in physical size. Moreover, the lens required would have to meet extremely rigorous and expensive conditions as to flatness of eld, diameter and other factors. The present invention provides large extremes of reduction and enlargement together with high optical speed, within a moderate physical size, and at comparatively low cost. These advantages are obtained whether the machine is used for the production of engravings as described, or whether it is employed to produce a photographic reproduction in the fashion of ordinary facsimile equipment.

In order to provide proper signals from the photocell for all values of enlargement and reduction, it is also necessary to provide an appropriate adjustment of the effective physical aperture of the scanning system. This adjustment is made automatically by mechanism also illustrated in Fig. 3, in connection with the adjustment of the linkage to define the proper scanning arc. With all of these considerations in mind, a detailed description will now be given of the mechanisms shown in Figs. 3 and 4.

The drive motor for the entire machine is indicated in Fig. 3 by numeral 64 and is a known type of two-speed motor providing speeds of (in this instance) 1725 and 1125 R. P. M. at its output shaft 66. Shaft 66 carries a worm 68 (Fig. 4) meshing with 4a worm wheel 70 on the 6 main shaft 36. The main shaft and the cylinder 22 thus rotate in the direction indicated by arrows thereon at speeds proportional to the speed of the motor 64.

Shaft 36,'Fig. 4, is provided with a worm 72 which. engages with worm wheels 74, 76 at opposite ends of a diameter of the worm 72, these worm wheels serving to rotate in opposite directions their respective shafts 78 and 80, and the worms 82 and 84 carried thereby. The last named worms are provided with opposite pitch, so that they drive their respective mating worm gears 86 and 88 (the same having different numbers of teeth) in the same direction. Each of the gears 86 and 88 is selectively connectable to a shaft 38 by clutch 94 controlled by a knob 96 which is rotated to the rightto engage the gear 86 for -screen cutting, or to the left to engage gear 88 for making 120-screen plates. The other end of shaft 38 carries a wheel or pulley 98 about which passes the inextensible tape or ribbon 40 held taut by another wheel or pulley 100 provided with a suitable spring biasing device 102. The carriage 16 has the clamp 44 mentioned above as connecting the carriage with the tape 40, whereby the carriage is caused to move along the axis of cylinder 22 to cause the cutter head 18 totrace out a helical path upon a sheet secured to cylinder 22, in the manner described in the Boyajean patent.

As also shown in Fig. 4, the motor shaft 66 carries at its end a helical pinion 104 mating with a similar helical pinion on a shaft 106 whose upper end is secured to a flat disc 108. A ball assembly 110 is in contact with disc 108, and transmits motion to a cylinder 112 by frictional contact with both the disc and cylinder, the axis of cylinder 112 being perpendicular to and intersecting the axis (extended) of shaft 106. The radial position of ball assembly 110 with respect to disc 108 is controlled by a micrometer positioning device 114 suitably secured tothe framework of the machine, and connected to the ball assembly by a rod 116.

The parts just described constitute Ian adjustable vari able-speed transmission between the motor shaft 66 and the shaft 118 carrying cylinder 112. Said shaft 118 also carries a worm 120 engaging a worm wheel 122 on a stub shaft which has secured to its other end a worm 124, see Fig. 3. A worm wheel 126 engages Worm 124 for rotation at a speed determined by the micrometer adjustment 114, and is associated with a clutch 128 controlled by manual knob 130 so as to drive a vertical shaft 45 mentioned above and shown also in Fig. 2, at the selected speed when clutch 128 is engaged. At its lower end shaft 45 (see now Fig. 4) carries the wheel or pulley 46 about which passes the other inextensible tape or ribbon 48 held taut by a wheel 138 which is provided with tensioning means similar to that provided for tape wheel 100. The moving table 30 carrying the original to be scanned is connected to one portion of the tape 48 as by a clamp 142, and it will be clear from the above that the table will therefore be moved in the direction of the arrows shown thereon at a speed, relative to the rotation of cylinder 22, selected by the micrometer adjustment 114.

The parts of the above mechanism which are included in the transmission housing 26 of Figs. 1 and 2 are shown as lying within a dot-dash outlined compartment, in Figs. 3 and 4, this compartment being designated by the same reference numeral 26.

Referring now back to Fig. 3, it will be seen that the shaft 36 has the portion 36 extending to the left of transmission 26, and it carries the record drum 58 for rotation therewith. In the present machine, as stated, the drum carries three tone generating tracks 144 to provide proper pulse spacing for four combinations of screen spacing and engraving size. Adjacent and to the left of tone wheel 58 is the manually controllable clutch 50 which permits the cylinder 22 and tone wheel 58 to be operated to make a sample cut while the scanning mechanism is disabled, so that a sample cut or engraving :each cooperates with one of the tone tracks.

7 derived. fromV one, or more selected spots ofthe original copy can be accomplished. When clutch 504 is engaged, the shaft 52'will rotate, andV drive the scanning mechanism to be described-below.

TheV parts of theabove mechanism which are included originaLand contained inl the housing 34- of Fig. l, lie t theleft ofthe record drum 58, the latter being situated between the housings V26 and 34. However, in practice, the drumrSS iscovered by an outer casing which also covers the mechanism housing 26.

Before describing the` scanning mechanism inV detail, the means by which the machine provides proper displacement of thek engraved dots on the nal engraving, as between successive lines of dots, will be referred to in connection with Fig. 5. 1n this connection, it will be understood that thedesired diagonal or 45 pattern ofjengraved; dots is accomplished by eectively shifting the position yofall the dots in ,eachl alternate row or line, a, half-dotspace (lengthwise ofthe line), so that the dotsoccupy positions intermediate the positions they wouldV havel hadV if they had notbeen so shifted. Since the positions ofthe dots along any line are determined by the tone pulses derived from the record tracks on drumk 58, this could be accomplished` by rotating the drum with respect to its shaft a distance of one-half the spacing of theY tone pulses. in the present machine, howevenmechanical complication is reduced by utilizing a separate magnetic pick-up head for each row of teeth or tone track on the tone drum, and electrically reversing the output polarity of the pick-up head during alternate revolutions of the drum and cylinder 22. The alternate teeth and spaces of each tone track passing in proximity to the pick-up head produce a variation in the air gap of a magnet circuit including a voltage pick-up coil and a small permanent magnet both contained in each pick-y up head. The polarity reversing switch producesk an eiective phase shift of 180 in the resulting tone frequency output voltage. in order to minimize small errors in the shape of individualteeth on the drum, the pick-up head may actually include a number of spaced pickup points so that the reluctance vvariations of several drum teeth will be averaged in the output of the pick-up in a manner which is well understood in the art.

As shown in Fig. 5, one of the pick-up heads already described is indicated at 146, and a second and a third pick-up head are carried on the same` support 152 which is held in xed position relative to drum 53. There is a pick-up head for each of the tone tracks on drum S, and the heads are displaced in the axialdirection so that The heads may obviously be spaced circumferentially, as in Fig. 5, for clearance reasons. The switching arrangement for reversing the polarity o-f pick-up 146 is indicated in Fig. 5, a similar arrangement'being provided for each of the heads. To accomplish this, the following mechanism is provided. Shaft 52 carries a gear 154 meshing with a gear 156 having twice the number of teeth, so that gear 156 rotates once for each two revolutions'of the shaft 52. Gear 156 is xed on a shaft 1158 carrying a cam 160 whose follower 162 operates a switch rod 161i controlling a. reversingvswitch 166 which directs the output from head 146, withV one polarity, to the modulator 62 or intervening amplifier (not shown) during one revolution of shaft 52, and reverses the polarity of the output during the next following'revolution of the shaft 52. The change-over or actual switch operation occurs during a brief intervalof rotationof cylinder 22 when the joint or plate clamping region ofthe plastic sheet is passing under the engraving stylus,V so that when the plate is removed from the cylinder, the change-over portion is outside the useful area of the engraved plate. may bea switch 166 for each pick-up, or the outputs `of the pick-ups may be manually switched to single reversing switch 166.v

Basically, the scanner comprises means: for-rotating the .s

There 8l scanning mirror through a, predetermined angle which is centered or distributed equally on opposite sides of a common zero-deection position in which the mirror is scanning a spotV o n Vthe longitudinal center line ofthe copy table 31).

'ze of this angle to scan originals of 'dilierent sizes. To this end, the shaftA 52, whichV rotates at the same speed as the engraving cylinder when clutch 5t) is engaged, terminates at its forward end (Fig. 3) in a cam disc 168 which engagesa follower roiler 170 constrained to oper-A ate in a verticalV straight line by reason of the fact that its axle 172 is mounted between spaced links 174 forming the center links of a straight line linkage including the upper and lower parallel links 176, 178 whose outer ends are rotatable'upon` axes xed with respect to the machine frame. The fixed axisV shaft of the upper links 176 is indicated inlig. 3 at 18d,

Pl'he vertical motion of cam follower 17? is transmitted into rotation offV a leyer 1,352 by reason-ot the sliding engagement of one endcfsaid lever with aslide block 154 supported by the axlev 17.2 of follower 176 and hence partaking of its vertical motion.V Lever 182 is biased into contact with the block 184 as by a tension spring 186 extending to a xed partof the machine. To convey the rotation of lever 182 forward to operate the scanning reflector 54, lever 132 is connected to or integral with a yoke body 188 having two outwardly extending arms'.v

190, 192 rigid therewith, the pivot axis of ,lever 182, yoke body 18S and arms i90', 192 being indicated at 194, and fixed with reference to the machine frame.

The upper edge of each of arms l9t, 192 formsfa sliding support surface for a respective follower block 196,V 198, carried upon a common axle 200 whose ends are secured to the spaced central links 2%2, ZM of another Y. straight-line linkage to constrain the blocks and axle to Thus, one end of linl;A 262 is pivoted to the-end link 2il6rand the other end to.

move in a straight vertical path.

ship with aiixed guide rod 218. End links 206 and 203 of the straight-line linkage are duplicated to connect the link 204 with rods 210 and 212 so that axle 260 will be,`

maintained in properA position and supported against displacement except inthe desired vertical path.

Between slide follower blocks 1% and 198, the axle 260 carries a slide block 22t-which will therefore also.

partake of the vertical motion ofaxle 20G, and this slide block 229 rides along the under surface of a lever 222 to rotate theilatter and thereby the shaft-224 secured to said lever, said shaft being in fixed position on the machine frame. At one end,` the shaft 224 carries a drive sector,

226, one point on whose-periphery has attached thereto a short flexible and inextensible (metal) strap or belt 228.v whose other end is secured to a point on the periphery of a driven sector 23d. The sectorstransmit the rotation of shaft 224 to the scanning mirror'54, and it will be observed that the movable axle 206 operates as an adjustable fulcrum between the axesl 194 and 224. Fig.Y

6 of the drawings shows this portion of the mechanismV to a larger scale and in fragmentary vertical section for ready understanding.

The shaft carrying scanning 232, and is supported in bearingstnot shown) secured to the machine frame. ireely about this shaft, as by a bushing, and has an upstanding arm 234biassedby spring 236'and having an extension arm 238 cariying an adjusting screw 240 abutting againstia lug 242 secured to the mirror shaft 232. A spiral spring, 244 connects lug 242 with the driven section` 1 230 to permit a zeroadjustmentfof the mirror position` Means are provided for adjusting theV mirror 54 is indicated at.

The driven sector 236 is journalled` by screw 240; that is, screw 240 permits the central position of the scanning mirror to be set to correspond precisely with the direction of the center line of the copy board or table 30, and of any copy centered thereon. Spring 236 eliminates backlash in the lever and sector system and maintains lever 222 against the block 220.

From the above description, it will be realized that the amplitude of excursion of the scanning mirror from its central'position will be determined by the lateral position of axle 200, and that this is regulated by the lateral position of carriage 214. To accomplish the desired carriage motion, the lead screw shaft thereof terminates in a pinion 246 meshing with a pinion 248 rotatable by a shaft 250 whose opposite end has secured thereto the ratio-adjusting crank disc 252 located at the control panel of housing 34. The adjustment itself is indicated by a dial indicator 254 located adjacent the crank disc and connected by suitable gearing to a shaft indicated by numeral 256 and carrying a gear 258 meshing with a pinion on shaft 250. Shaft 256 also is geared to a wide pinion 260 with which meshes a pinion 262 forming part of the double-range adjustable square aperture device 264 which forms a part of the optical system of the machine, being disposed at the back focus of the lens system, slightly ahead of the phototube. For the present, it will suffice to say that the wide pinion 260 permits a control shaft assembly 266 to be moved axially between two positions corresponding to the two screen or dot spacings provided, the precise adjustment within the range for any one screen being controlled from the ratio crank disc 252. A more detailed description of this mechanism will be given hereinafter.

While the parts described above provide for the desired adjustment of the angular travel of the scanning mirror, and ensure its proper speed relation to the rotation of the engraving cylinder, it is necessary also to provide correction for the change in distance from the scanned spot of the copy to the scanning reflector as the spot moves from one extremity of a scanned line, through the central position, and thence to the opposite end of the line. To understand the operation of this part of the machine, the optical path of the scanning operation must be understood. As best shown in Fig. 3, light rays arriving from the scanned spot of the original copy are deflected by scanning mirror 54 through a cyclically moving focussing lens 266, a fixed lens 268, reflectors 270 and 272 to a beam splitter or semi-reflecting mirror 274. All of these parts except lens 266 are fixed with reference to the machine housing. The beam splitter 274 reflects a portion of the light received from the copy to the photomultiplier cell 56, via the controllable aperture device 264 to be described below. The beam splitter 274 also permits light from an auxiliary source 276 to be directed, after passing through a prism and reticle combination 278, back along the path just described and reflected by scanning mirror 54 onto the original copy. The reticle and associated optics produce a small spot of light on the copy, corresponding to the position occupied by the reflector 54 and of course the copy table 30, so that during an initial measuring or set-up period, prior to making an engraving, the photocell output can be determined for any selected, or successively different, spots on the' original copy. Thus machine, amplifier and stylus motor adjustments may be made with the engraving portion of the machine operative, and the engraved sheet under inspection, but with a particular spot producing the signal, as described above. Light source 276 is turned olf before the making of the .test engraving or the actual nal engraving is commenced. v

For reasons associated with the fact that the sheet or plate being engraved is wrapped about cylinder 22, with an unused portion at the clamping or joint area adjacent opposite edges of the sheet when the latter is in position on the cylinder, the scanning operation across the original copy is made to produce useful electrical output in only one direction. That is, the actual scanning of one line is followed by a rapid retrace of the scanning beam (the viewing axis of the scanning reflector as clearly shown in Fig. l) across the copy, after which the next line is scanned, and so on. This rapid retrace is accomplished by the shape of cam disc 16S whose radius rises smoothly during nearly an entire revolution, and then falls sharply at the end of one line scan. The output of the photocell 56 during the retrace interval is ineffective, insofar as the finished engraving is cond cerned, because the retrace interval is arranged to occupy the time when the engraving stylus is passing over the clamping region of the sheet being engraved.

With the above scanning pattern in mind, it will be seen that during one motion of the scanning vmirror from one margin to the other of the original copy, the distance from the scanned spot to the reflector will first gradually decrease, until the spot lies on the central axis of the copy, and then will increase again until the opposite margin is reached. Since the distances corresponding to both margins are identical (the copy being centered below the axis of mirror 54), the next scanning line commences with the same copy-to-mirror distance as obtained when the opposite margin was reached at the end of the previous line.

The focussing operation is controlled from the lever 222 which has a tail portion carrying a cam roller 280 which rides against the cam surfaces of two arms 282 and 284. A fixed journal block 286 carries parallel rods or axles 288 and 290, and rod 288 is pivotally connected at one end by a link 292 to a latch bar 294 carrying the upwardly extendingA arm 282. A link 296 pivotal- 1y connects one end of rod 290 to an intermediate portion of latch bar 294, so that the latter can move parallel toitself through a limited longitudinal distance. A link at the other end of rod 288 is pivoted to a frame bar 298 which is bent at its other end to carry the arm 284 which extends downwardly therefrom. One end of rod 290 carries a link 300 pivoted to an intermediate portion of frame bar 298, and a portion of this link 300 extends upwardly as at 302 and is connected via linkage 304, 306 and 308 to the mount of focussing lens 266, suitably guided for rectilinear movement along its axis by a rod 310. A tension spring 312 urges latch bar 294 toward the cam roller 280.

Now consider the positions of the parts when commencing to scan a line of the original, with the roller at its lower position on cam disc 168, when roller 280 will be at its topmost position. As scanning commences, roller 280 will move down, and will urge arm 282 against the tension of spring 312, and by engagement of latch 314 (now engaged) will move to the left a rod 316 carrying said latch. A second latch 318 mounted on the machine frame is disengaged at this time. Rod 316 is secured to arm 298 and hence will move the latter to turn lever extension 302 so as to move focussing lens 266 towards the xed lens 268 to maintain the scanned spot in focus at the photocell 56.

When the cam disc 168 has turned suiliciently to put the parts in the Fig. 3 position, the reflector 54 will have turned so that a spot directly under its axis is being imaged at the photocell, and roller 280 will be in the position shown, but still moving downwardly. At this time, latch 318 engages the latch bar 294 and prevents it from moving forward under the tension of spring 312, and latch 314 becomes disengaged. As roller 280 moves downwardly, it will pull upon the downwardly extending arm 284 and move the frame bar 298 forwardly, thus rotating lever extension 302 to restore the lens 266 to its starting position, the lens reaching its position farthest from lens 268 as the end of the scanned line is attained.

The limit of forward travel of frame bar 298 is set by a stop screw 320 engaging the periphery of a cam 322 free Ato rotate on the shaft 224, its position being controlled in accordance with the pre-adjusted ratio adjustgevaarte 11 mentby reason vofv a rod 324i on carriage 214 engaging in the slotted tail portion 326 of cam 322.

During the retrace interval, as roller 280 startsto move inwardly, to the position shown in Fig. 3, downward arm 284 is free of roller 280 and remains stationary, as does lens 266. Since latch 318 is still holding latch bar 294 against forward movement, the roller 280 continues to move up without affecting the position of lens 266, because although latch 318 is disengaged at some time during the retrace and releases bar 294, the latch bar 294 moves idly without affecting frame bar 298 because of the pin-and-slot lost motion connection' indicated between frame bar 298 and the rod 328 carried by latch bar 294. Hence, the parts arrive at the position corresponding to the next scanning line in the condition from which they started to scan the previous line.

The operation of the latches 314 and 328 is controlled in timed relation to thev rotation of shaft 52 by means of a cam 330 on said shaft, cooperating with a follower bar 332 and linkage 334 controlling the vertical positions of two control rods 336, 338, the former being pivotally connected to latch 318 to raise and lower the same, and the latter being received in a slotted tail portion of latch 314 to control the latch in any position of latch bar 294.

A more detailed description will nowv be given of the operation of the aperture adjusting means 264 of Fig. 3, which is shown to larger scale in Fig. 7 of the drawings. As in the previous ligure, numeral 260 designates a wide pinion driven by gearing from the ratio crank 252, so that the shaft 266 will be turned whenever the ratio of enlargement or reduction is altered by movement of the carriage 214. The wide pinion meshes with a pinion 262 which has a iiattened segment as shown, and is xed against slidable motion along the shaft but is free to turn on the shaft as a bearing. A sleeve 340 loosely encircles the shaft 266 and has secured thereto a bracket 342 connected to the gear 262 by adjusting screws 344 engaging the liattened portion of the gear. These screws enable a precise relation to be established between the angular position `of the pinion and the angular position of the sleeve 340, which carries at its forward end a cam 346 which therefore rotates with pinion 262, while shaft 266 can be moved axially, as indicated by the arrow in Fig. 7, to move shaft, sleeve and cam axially in the same direction.

The physical aperture of the scanning system is defined by the mechanism generally designated 264, and includes a pair of diaphragm elements 348, 350 shaped to form together a cats eye aperture 352, and located at the back focus, of thelens system, from which the rays diverge slightly to the cathode of the photocell 56. The size of the aperture can be varied by rotating one diaphragm with relation to the other, the aperture shape remaining substantially rectangular within the small range of adjustments required. The thin diaphragm el'e ments are closely adjacent one another, the forward onein Fig. 7 being secured to a shaft. 354 passing through a sleeve 356 to which the other diaphragm element is secured. Shaft 354 has its rear endclamped in a crank element 358, and sleeve 356Y is clamped in a similar Crank 360, the cranks being split as shown and provided with clampingscrews for initial adjustment of the diaphragm element angular positions. TheA sleeve 356 will be journalled in a iixed partof the machine to maintain the center of the aperture 352 in proper centered position with respect to the optical axis of the scanning system.

Each of the cranks 358 and 360is providedwith a respective cam follower control rodV 362, 364 generally paralleling shaft 266 and having an enlarged portionnear its end engagingV the periphery of the camj disci 3.46. Springs, not shown, maintain the cam follower control.

rods against the cam periphery.;- The rotationA of camA 346 by pinion 262; will thus move thecontrolrodsto rotate both diaphragm elementsk (in respective opposite directions) to adjust the size of aperture 352 in accordance with the enlargement or reduction ratio dictated by the position of carriage 214. The cam 346 is shaped to provide the. desired functional relationship between aperture dimensions and enlargement or reduction ratio, e. g. for the making of 120 screen plates.

In order to provide a similar functional relationship for the case in which coarser screen engravings are desired, for example screen plates, shaft 266 is pushed inward, as by a control knob 366 thereon, to slide pinion 262 along pinion 260, whereupon the cam 346V moves to engage portions of the control rods 362 and 364 nearer the cranks 358 and 360, cam-engaging enlargements being provided at these inner points of the control rods, as shown. Since the shape of cam 346 remains unchanged, the only result is to increase the mechanical advantage of the leverage, so that the aperture 352 will be opened to a proportionately larger aperture size when cam 346 is in its inner location. The forward end of shaft 266 is slidably supported in a fixed machine part 368, and may be grooved at two points (one designated 370 in Fig. 7) to define the working positions of cam 346 by reason of frictional engagement of a spring-pressed ball snap 372 carried by part 268 and engageable within the respective grooves to provide a definite and feelable position adjustment of the shaft 266.

While the particular dimensions, gear ratios and the like may be varied widely to accommodate different enlargement and reduction ratio limits, different screen spacings and so on, a representative setY of relationships will be tabulated here, the same being those pertinent to the particular exemplary machine shown in the drawings. The dimension X in the table is the center-to-center distance from thev pivot axis 194Y (Fig. 3) to the axis of shaft 200, and hence represents also the position limits of carriage 214 for various size change ratios.

TABLE AND CARRIAGE TRAVEL PER REVOLUTION OF CYLINDER 22 Y Table 30 travel Carriage 16 travel Size ratio 85 screen, 120 screen, 85 screen, 120 screen, inches inches inches inches 8:1 0. 0010 0.0007 0. 0083 0. 0059 1:1 0.0083 0.0059 same same 1:4 0. 0375 0. 0265 same same The diameter of cylinderv 22 may be 2.843 inches for the high speed (50 R. P. M.) operation, and 3.998 inches for the low speed ('33 R. P. M.) speed. The record drum 58 may have three tracks, one carrying 765 tone cycles for screen operation using the smallerV cylinder 22, and for 85 screen operation using the larger cylinder 22. The other two tracks will carry 1075 cycles for 120 screen' operation with the larger cylinder, and 545 cycles for 85 screen operation with the smaller cylinder.

Some further explanatory remarks will serve to clarify the reasons for the type of scan linkage employed herein; ToV make an engraving having no distortion in dimension. in` relation to theoriginal copy except magnification or` j reduction asdesired, it is necessary for the-scanning beaml to travel across the copy in uniform linear increments in ratio to uniform linear increments of motion of the engraving plate under the stylus. To accomplish this, it is imperative that the scanning beam move, not in equal angular increments related to cylinder rotation, but so the tangent of the angle the scanning beam makes with the perpendicular centerline is in constant ratio to the angular movement of the cylinder.

To accomplish the above effect, the mechanism shown in Figure 6 was devised. Cam 168 (fixed rotationally to the cylinder shaft 36 during scanning) and having al uniform rise for each equal angular increment, is used to drive the scanning mirror. The cam follower roller 170 is constrained by a straight line linkage (not shown in Figure 6) to travel in a line radial to the cam center, thereby imparting a uniform linear movement to the roller shaft 172. By means of the two sliding shoes pivoted on roller shaft 172, this motion is transferred to pivoted lever 182 which thereby moves so the tangent of the angle the lever makes with a horizontal line varies in direct ratio to the angular motion of the cam and cylinderand has a fixed total movement for each revolution of the Acam 168. Fixed to lever 182 is yoke 188. vLifted by the yoke is the pair of sliding shoes 196, 198 constrained to move in a straight line, parallel to the line of movement of cam roller 170, by the linkage shown in Figure 3. The position of these shoes is adjustable along arms 190, 192. Actuated by a third shoe 220 carried on shaft 200 is the lever 222. The distances X and Y, as determined by the position of shaft 200 in relation to the fixed pivots of levers 190 and 222, determine the ratio of the angular movement of lever 222 to lever 190. However, the angular movement of lever 222, as determined by the preceding conditions, is such that the tangent of the angle varies in a constant ratio to the rotation of the cam 168 for any given position of shaft 200. The angular movement of lever 222 corresponds exactly with the angular movement of the scanning beam. However, since the scanning beam is reflected by a mirror, its angular change is twice as much as the angular movement of the mirror. Therefore, to make the angular movement of the mirror equal to one half the angular movement of lever 222, lever 222 has fixed to it sector 226 of radius "r. Rigidly aixed to mirror 54 is sector 230 having a radius R,

equal to twice radius r. Connecting the two sectors is tape 228, transmitting the angular movement of lever 222 to the mirror, but dividing the angular movement by` two, due to the ratio of the radii of the sectors. The tape drive is used in preference to gears to insure a smooth, vibrationless drive between the lever and the mirror. The mirror is so mounted that its reflecting surface lies in the same plane as the axis of rotation of the mirror, to eliminate any shifting of the scanned spot from its correct position. The entire system of levers, followers, etc., is biased by spring 236, which eliminates backlash and furnishes the power to restore the system to its starting point during the return portion of the cam.

From the foregoing, it may be seen that the original requirement of uniform linear travel of the scanned spot in direct proportion to the travel of the engraving sheet under the stylus has been met by utilizing the tangent functions of the various members, rather than their angular movements, except for the final mirror drive which requires a division of the angular travel due to the angle-doubling reflecting characteristics of a mirror. The invention has been described above in consider. able detail, and particularly with reference to its application to the making of engraved plates either for direct use in a printing operation, or as matrixes for duplication by the well-known stereotype processes. However, it will be apparent to those skilled in the artthat the invention is also applicable to the making of reproductions of the original matter in forms other than engraving plates. For example, the cylinder 22 may carry a photo- Sensitive or photographic material, and instead ofan engraving cutter or hot stylus type of transducer, the carriage l6 may carry an output transducer which directs a beam of light upon the photosensitive sheet to produce a photographic type of image in response to the signals derived from the scanning mechanism. Again, the sheet carried by cylinder 22 may be of a suitable plastic or the like which can be locally hardened by the light emanating from the transducer, to produce a sheet which can be then treated after the manner of photo-engraving processes to produce a direct printing element. Hence, the invention is not to be considered as limited to the particular details given, nor to the specific application to which reference has been made during the description of the apparatus, except insofar as may be required by the scope of the appended claims.

What is claimed is:

l. In a photoelectrc image reproducing machine, a copy support movable in a straight line in one direction, a fixed scanning head including an optical system having an oscillatable optical element for imaging successive elemental areas lying along a line on said copy support perpendicular to said direction, photoelectrc means for converting the light output of said optical system to electrical signals, an adjustable aperture device for controlling the size of the elemental area imaged by said optical system, means 'for supporting a sheet to be treated from point to point in accordance with said electrical signals to reconstitute the subject-matter of the original copy, an output transducer energized by said signals and mounted for movement over a sheet carried by said supporting means to treat the same in a pattern corresponding to said signals, first adjusting means for simultaneously adjusting the amplitude of oscillation of said optical element and the said adjustable aperture device, and second adjusting means independent of said first adjusting means for adjusting the speed of travel of said copy support relative to the speed of movement of said output transducer over said sheet.

2. In a photoelectrc engraving machine, a copy support movable in a straight line in one direction, a xed scanning head including an optical system having an optical element oscillatable through a limited arc for imaging successive areas lying along a line on said copy support perpendicular to said direction, means for moving said copy support in timed relation to movement of said element, photoelectrc means for converting the light output of said optical system to electrical signals, an adjustable aperture device for controlling the size of the area imaged at each position of said optical element, means for supporting a sheet to be engraved from point to point in accordance with said electrical signals to reconstitute the subject matter of original copy, an output engraving transducer energized by said signals and mounted for movement over a sheet carried by said supporting means to engrave the same in a dot pattern corresponding to said signals, first adjusting means for simultaneously adjusting the amplitude of oscillation of said optical element and the said adjustable aperture device, and second adjusting means independent of said first adjusting means for adjusting the speed of travel of said copy support relative to the speed of movement of said output transducer over said sheet.

3. In a photoelectrc image reproducing machine, a copy support movable in a straight line in one direction, a fixed scanning head including an optical system adjust- 'able for focus and having an optical element oscillatable through an arc for imaging successive areas lying along a line on said copy support perpendicular to said direction, photoelectrc means for converting the light output of said optical system to electrical signals, an adjustable aperture device for controlling the size of the area imaged by said optical element, means 'continuously adjusting said optical system to maintain focus as said element oscillates through said arc in one direction only, means for maintaining said optical system in fixed adjustment during, movement of said element in the opposite direction, means for supporting a sheet to be treated from point to point in accordance with said electrical signals to reconstitute the original copy, an output transducer energized by said signals and mounted for movement over a sheet carried by said supporting means to treat the same in a pattern corresponding to said signals, rst adjusting means for simultaneously adjusting the amplitude ofV oscillation of said optical element and the said adjustable aperture device, and second adjusting means independent of said rst adjusting means for adjusting the speed of travel of said copy support relative to the speed of movement of said output transducer over said sheet.

4. In a photoelectric image reproducing machine, an optical system including an adjustable aperture device for scanning an original to produce signals representing the instantaneous tone values of successive points of said original along thev scanning line, progressively movable means for locally treating a sheet to produce a representation corresponding to said signals, means for adjusting the effective scanning speed of the scanning system, and means controlled by said adjusting means for altering the adjustable aperture device of said optical system in accordance with the adjusted scanning speed.

5. in a photoelectric engraving machine, an optical system including an adjustable aperture device and having a rotatable element for line scanning an original to produce signals representing the instantaneous tone values ofi successive points of said original along the scanningline, progressively movable means for engraving a sheet with a dot pattern corresponding to said signals, means for adjusting the effective linear speed of movement and the scanning travel of the scanning element, and means controlled by said adjusting means for altering the adjustable aperture device of saidoptical system in accordance with the adjusted scanning speed.

6. In photoelectric image reproducing apparatus of the type including means `for scanning an original to develop electrical signals, means for progressively treating a sheet in response to the instantaneous magnitude of said signals, andmeans for altering the relationshipl between the size of the scanned original and the size of the reproduction so produced; the improvementV comprising signal tone generating means for producing selectively one of av plurality of modulating tones having iixed frequencies independent of the speed of said scanning means and of said treating meansto modulate said signals, and means for. selecting and applying to said developed signals a particular one of said tones in accordance with the desired dot pattern to `be produced on said sheet.

7. In photoelectric engraving apparatus of the type including means for scanning an original to develop electrical signals, means for progressively engraving a printing plate with discrete engraved data in response to the instantaneous magnitude of said signals, and means for altering the relationship between the'size of the scanned original and the size ofV the engraving so produced; the improvement comprising signal tone generating means for producing selectively one of a plurality of modulating tone frequencies,` each ixed and independent of the speeds of the scanning means and of the" engraving means, to dot modulate said signals, means for selecting and applying to said developed signals a particular tone frequency output in accordance with the desired dot patern to be engraved on said plate, and means for periodically phase-shitting said tone frequency output to alter the position of the dots produced on said plate.

8. Photoelectric engraving apparatus includinga copy holder'mounted for linear movement in oneV direction, an optical system including an oscillatable beam-deiiecting meansv for scanning material on said'holder along successive lines perpendicular to said direction, meansfor deriving from said optical system electrical signals representative of copy density from point to-pointalong each 16 of said successive lines, and means for adjusting concomitantly the speed and the amplitude of said' scanning motion for scanning copy of a predetermined size, to produce signal trains of fixed duration corresponding to each of thesuccessive scanned lines.

9. Photoelectric engraving apparatus including a copy holder mounted for linear movement in one direction, an optical system including an adjustable aperture device and anl oscillatable beam-deflecting means for scanning material on said holder along successive lines perpendicular to said direction, photoelectric means for deriving from said optical system electrical signals representative of copy density from point to point along each of said successive lines, and means for adjusting concomitantly the speed and the amplitude of said scanning motion, and said aperture device, for scanning copy of a predetermined size, to produce signal trains of fixed duration corresponding to each of the successive scanned lines.

I0. A scanning system for photoelectric engraving machines, comprising a copy support movable-along a straight line in' one direction, an optical system including an oscillatable optical defleeting element for scanning copyI on said support in successive lines extending generally perpendicular to said direction, and meansv for adjustingwthe magnitude of movement of said deecting element symmetrically on both sides of a central position correspondingV to the center line of copy material on said support.

1l. A scanning system in accordance with claim 10;

including aconstant speed drive, a motion converting mechanism for converting movement of said drive into any oscillating movement of said deecting element, and means for adjusting the' said mechanism so as to Ialter the limits of movement of said deilecting element without changing the time period of each scanning cycle thereof; l2. A'scanning system in accordance with claim 11, including means for adjusting the eitective size ofthe elemental copy area covered by said optical system, and means for controlling concomitantly the ratio of said mechanism and the adjustment of said elemental copy area adjusting means. Y

1-3. A scanning system for photoelectric copy reproducing machines comprising `a copy support, an optical system including an oscillating ray deliector for scanning copy on said support in successive lines extending across said copy, an axially movable optical element movable to maintain focus during passage in -a rst direction of said deflector across said copy, a drive for swinging said' de-v ector at one speed to scan across said copy in said first direction and for swinging said dei-lector at a higher speed to return said deector, `a connection between said drive and said element for moving the latter during swinging of said deector in said iirst direction to maintain focus, and means for disconnecting said drive from said element during return motion of said deilector.

14. In a photoelectric engraving machine, an optical system including an `adjustable aperture device for scanning an original to produce signals representing the instantaneous tone values of successive points of said original along the scanning line, progressively movable means for engraving a sheet with a dot pattern corresponding to said signals, means for adjusting the eiective scanning speed of the scanning system, and means controlled by said adjusting means for altering the adjustable aperture device of said optical system in accordance with the adjusted scanningV speed.

l5. An optical system for use in the scanning of original copy to produce electricalV output signals therefrom in a photoelectric engraving machine, comprising a lensV system and a photocell positioned to receive light from said lens system, and an adjustable aperture device for limiting the size of the bundle of rays passingV to said photocell, saidV device including means for adjust'- :ing the size` oi said' aperture over two different ranges of sizes, and means for selecting the range of sizes over which the size adjustment is made.

16. An optical system in accordance with claim 15, in which said adjustable aperture device comprises diaphragm elements each having a pivoted position control element, in which said size adjusting means comprises a rotatable part engaging said elements to pivot the same about their axes, and in which said range selecting means comprises means for positioning said part at different distances with respect to the pivot axes of said elements.

17. ln a photoelectric image reproducing apparatus, a copy support, a scanning device mounted for rotation about an axis to scan copy on said support, a rotatable cylinder adapted to carry a reproduction sheet, a reproducer energized by signals from said scanning device for activating a sheet on said cylinder, and means for rotating said scanning device periodically to scan across the copy, such that the tangent of the angle traversed by said scanning device is maintained proportional to the angular rotation of said cylinder.

18. The method of scanning copy to produce electrical signals for transmission to image reconstituting apparatus to produce a reproduction of altered dimensional scale, comprising the steps of scanning said copy to produce signals representative of copy density from successive adjacent spot areas of said copy disposed in a straight line extending across the copy in one direction, repeating said step for successive straight lines disposed parallel to the irst mentioned line, and adjusting the amplitude of said scanning operation in accordance with the size of said copy in said one direction, to produce a group of signals of constant time duration corresponding to each scanning line.

19. The method of producing a facsimile of original copy but to altered dimensional scale, comprising the steps of scanning said copy to produce signals representative of copy density from successive `adjacent spot areas of said copy disposed in a straight line extending across the copy in one direction, repeating said step for successive straight lines disposed parallel to the iirst mentioned line, adjusting the amplitude of said scanning operation in accordance with the size of said copy in said one direction, to produce a group of signals of constant time duration corresponding to each scanning line, successively treating lines of a sheet of sensitive material in accordance with said signals to produce a facsimile reproduction of the original copy, and controlling the spacing of said lines on said sheet to alter the dimensional scale of said reproduction.

20. In a photoelectric image reproducing machine, a copy support, copy scanning means, and means mounting said copy support and said scanning means for relative movement therebetween in a iirst direction to expose said scanning means successively to points forming a straight line in said iirst direction `on copy held by said copy support; power means for intermittently imparting such relative movement to said copy support and said scanning means at a uniform velocity in said direction, drive means for progressively effecting relative movement between said copy support and said scanning means in a second direction generally perpendicu lar to said rst direction to cause the surface of copy held by said copy support to be completely scanned by said scanning means; image reproducing apparatus including means for supporting a sheet to be treated from point to point in accordance with signals received from said scanning means, an output transducer energized by said signals, means for driving said sheet supporting means and said output transducer for relative movements with respect to one another in two substantially perpendicular directions to treat a sheet held by said sheet supporting means in a pattern corresponding to said signals; and means for controlling the relative movements of said sheet supporting means and said output transducer in said perpendicular directions at adjustable ratios relative to the corresponding motions between said copy support and said scanning device.

2l. In a photoelectric image reproducing machine, a copy support, copy scanning means, and means mounting said copy support and said scanning means for relative movement therebetween in a rst direction to expose said scanning means successively to points forming a straight line in said iirst direction on copy held by said copy support; power means for intermittently imparting such relative movement to said copy support and said scanning means at a uniform velocity in said first direction, drive means for progressively eliecting relative movement between said copy support and said scanning means in a second direction generally perpendicular to said first direction to cause the surface of copy held by said copy support to be completely scanned by said scanning means; image reproducing apparatus including a cylinder for supporting a sheet to be treated from point to point in accordance with signals received from said scanning means, an output transducer energized by said signals, means for rotating said sheet supporting cylinder and for moving said output transducer axially of said cylinder to treat a sheet held by said sheet supporting cylinder in a pattern corresponding to said signals; and means for controlling the relative movements of said sheet supporting cylinder and said output transducer at adjustable ratios relative to the corresponding motions between said copy support and said scanning device.

References Cited in the tile of this patent UNITED STATES PATENTS 1,929,988 Owens Oct. l0, 1933 2,139,752 Holmes Dec. 13, 1938 2,149,487 Zilberman Mar. 7, 1939 2,421,637 McNabb June 3, 1947 2,422,398 Dilks June 17, 1947 

